Method of producing titanium-phosphoric acid catalyst



Martian on PRODUCING TITANIUM-PHOS- rrronic Acin CATALYST No Drawing.Application September 9,1953 Serial No. 379,290

6 Claims. (Cl. 252 -435) This invention relates to a novel process forthe preparation of acidic solid catalysts and the novel catalysts thusproduced. More specifically, this invention relates to the so-calledTifo catalysts and to a novel and improved process for theirmanufacture.

The Tifo catalysts are solid, acidic, complex catalysts containingtitanium, phosphorus, oxygen and hydrogen in chemical combination andhave been produced by a variety of techniques. The Tifo catalysts arelight gray, friable solids which may be employed as pellets or powdersand have shown high activities in various hydrocarbon conversions, suchas olefin polymerization, the alkylation of aromatic hydrocarbons byolefins, isomerization of alkyl aromatics such as xylenes, etc.

Tifo catalysts are insensitive to superheated steam and oxygen,resistant to swelling by solvents non-corrosive, mechanically andchemically stable, long-lived, and can be readily regenerated. The Tifocatalysts show little tendency to produce coke from hydrocarbon chargingstocks, to swell or plug, or to release phosphoric acid whenemployed inreactor beds.

Tifo catalysts have heretofore been prepared by the reaction of atitanium halide, particularly TiCl with orthophosphoric acid in molarratios sufficient to furnish a halogemhydrogen ratio between about 0.4and about 1 at a temperature above about 175 C. for a period of timesuificient to evolve the halogen content of the reaction mixture ashydrogen halide in a substantial proportion of at least about 90%, andpreferably at least about 96%, as described in Application for UnitedStates Letters Patent, Serial No. 323,517 of Harold Shalit and Arthur P.Lien, filed December .1, 1952, now Patent No. 2,772,244. The previouslyknown method is effective for the production of useful catalysts, butsuffers frorn the disadvantages of the high cost of TiCl and. the factthat hydrogen chloride is evolved from the reaction mixture,necessitating the employment of HCl-resistant'materials in the catalystpreparation equipment. As is Well known,

vHCl-resistant equipment is expensive and special equipment design,which limits its flexibility, maybe required.

Itis an object of our invention to provide an improved method for thepreparation of Tifo catalysts. Another object of our. invention is toprovide a process for the manufacture of" extremely hard, mechanicallydurable, .and analytically active Tifo catalysts. An additional objectis to provide mechanically stable Tifo catalysts exhibiting highcatalytic activity in hydrocarbon conversions such as the polymerizationof normally gaseous olefins andin olefin alkylation reactions. These andother objects of our invention will become apparent from the ensuingdescription thereof.

In accordance with our invention, a Tifo catalyst is manufactured bymixing titanium dioxide, for example in the form of .rutile,.anastase orbrookite, with triphosphoric acid or a mixture of phosphoric acidscontaining a substantial proportion (between about 10 and about 95weight percent) of triphosphoric acid, and heating the 2 doughy mixtureto a temperature at which a vigorous, rapid, exothermic reaction occurswith the liberation and escape of water from the reaction mixture. Theweight ratio of titanium dioxide to triphosphoric acid can be variedbetween about 0.1 and about 2, preferably between about 0.25 and about1.3. The doughy initial mixture of titanium dioxide and triphosphoricacid can be shaped, as by extrusion or molding, before heating to thetemperature at which the exothermic reaction occurs. The rapidexothermic reaction occurs at a tem perature of about 240 C. andreaction can be effected at about 240 C. to about 330 C., usually about250 C. in order to prepare a solid. catalytic material of increasedmechanical stability, the heating of the reaction mixture may becontinued to higher temperatures up to about 600 C., more often to about380 C. to about 400 C. The heating time can be varied fromabout 0.5 toabout 4 hours, preferably about 2 hours.

X-ray analysis of the Tifo catalysts produced by the process of thepresent invention indicates that they are substantially identical withcatalysts produced by the interaction of TiCL, with orthophosphoricacid. A typical Tifo catalyst prepared from Ti0 and commercialpolyphosphoric acid (47.8 weight percent H P O in 2:1 weight ratio wasfound to contain 21.3 weight percent of titanium and 25.6 weight percentof phosphorus.

The Tito catalysts prepared in accordance with our invention change thecolor ofp-dimethylaminoazobenzene from yellow to red and the color ofbenzeneazodiphenylamine from yellow to violet, employing the method ofC.

Walling, I. Am. Chem. Soc. 72, 1164 (1950). The color change of thefirst indicator shows that the Tifo catalyst surface has a pK less than3.29; the color change of the second indicator shows that the surface ofthe Tifo catalyst has a pK of less than 1.52. It will be apparent,therefore, that the Tifo catalysts are highly acidic.

Surprisingly, we have found that titanium dioxide does not react withmeta-, orthoor pyro-phosphoric acids to produce catalysts, i. e. theyare substantially inactive in catalyzing the polymerization of propyleneunder the standardized conditions employed in our experiments. Thus, ahard, solid material was prepared by heating a mixture of 20 g. of TiOand 40 g. of an acid mixture containing 49% H P O 45% H 1 0, and about6% HPO to 380 C. for 4 hours. This material was inactive in theattempted polymerization of propylene with about 8 weight percent of thesolid material at about 200 C. for 2 hours. Also, a material prepared byheating TiO- and P 0 in the molar ratio .of 3:2, which should yieldTi;,(PO proved inactive for propylene poly-- merization at about 190 C.

As an example of our improved preparation of the Tifo catalyst, we mixed79.9 grams of titanium dioxide and grams of commercial polyphosphoricacid having the following composition:

Percent Meta-phosphoric acid (HPOg) 3.6 Triphosphoric acid (H P Om) 47.8Pyrophosphoric acid (H P O- 28.6 Orthophosphoric acid (H3PO 20.0

at room temperature and heated the mixture without stirring to 250 C. inan open reaction vessel under a hood. At 250 C. a vigorous exothermicreaction wasobserved, as indicated by a sudden rise in the tempera--ture of the mixture and the evolution of water. Theexothermic reactionwas soon completed, following which heating of the reactionmixture wascontinued to 380 C. The total elapsed time was 4 hours. The molar ratioof titanium dioxide to gramatom of phosphorus inthe reaction mixture wasabout 1.1. The reaction yielded a solid H PO., I 32.3 H4P2O7 ..I 5 3 1027.0 HPO 1.8

The mixture was heated to 340 C. for 3 hours. Aphard, dry catalyst wasproduced. A magnetically-stirred autoclave of 250 ml. capacity wascharged with-5 grams of this catalyst and 61 gramsof propylene andheated with stirring at 210 C. for 2.5 hours to yield 18.5;g, of liquidpropylene polymer, corresponding to 30 Weight percent conversion of thepropylene charged.

The relative inactivity of solid materials produced by the reaction oftitanium dioxide with other jphosp horic acids, as compared withpolyphosphoric acid,-is. shown in the following table:

Table 1 Temp. of 'Percent TiO /acid, Catalyst? "Propylene Catalyst from-(by wt.) Prepara- Polymertion, 0. ized at 7 Q 190 metaphosphoric acidand Ti01. 1 -380 V 0 orthophosphoric acid and 'IiO; 0. 290 y 4 6. 6orthophosphoric acid and TiO, 0. 5 400 i about 5 polyphosphoric acid andTiO 0.-5- -380 I Y j 53. 5 polyphosphoric acid and T109; 0. 5 350 73 1weight percent catalyst, based on propylene charged and 4 5 hoursreaction time. The slight polymerization activity of the solids preparedfrom TiO andorthophosphoric ,acidis ascribable to the fact that the acidwas somewhat aged and consequently contained a 111311 proportion oftriphosphoric acid. I r

We havefouud thatjthe activity of the, Tifo catalyst in thepolymerization of propylenefvaries with the ratio of "titanium dioxidetotheii iphosphoric acid employed in its preparation. This fact isindicated by the following tabulation in which the ratio of reagentsused to prepare the catalysts is related to propylene polymerizationactivity expressed by the average propylenefpressure, drop per minute inthe first two'houirs of the propylenepolymerization reactionsetfectedvwithrthe various catalysts.

Table -2 Tim/commercial polyphosphoric acid}; (by wt.) sure -Drop,lbs/min. in

first 2 hours used in its preparation? 7 There is some-evidenceftoindicate theta: Tito-type catalystcan be produced by the irea ction ofTiOg with a mixture F 9 .en f FQri w e wh c tth infer n m b th t thes urredvttiaa f dah Average Pres- F v 4 phoric acid. Thus, a mixture wasprepared of 20 g. of anhydrous H PO 10 g. of P 0 and 15 g. of TiO whichmixture was heated at 380 C. for 4 hours to produce a solid catalyst.The catalyst was tested for the polymerization of propylene employing 10Weight percent, based on the feed, at 200 C. in a stirred autoclave. Thepropylene pressure drop at the end of one hour was lbs. At the end of 2hours, 23 weight percent propylene conversion to polymers was obtained.The catalyst was dry and solid but not as hard as some of the Tifocatalysts derived from the reaction of TiO with commercialpolyphosphoric' acid.

The Tifo catalysts prepared by the present process were tested inhydrodesulfurization reactions. A Tifo catalyst was prepared fromtitanium dioxide and a commercial polyphosphoric acid mixture (47.8 w.percent H P O in the weight ratio of 0.5 and tested for vapor phasehydrodesulfurization of ,West Texas virgin naphtha containiug 0.319 W;percent sulfur at 400 C., 1000 p. s. i. hydrogen pressure and liquidhourly space velocity of 2. In one run, 58.6%. desulfurization and in asecond, 67.5 desulfurization of the naphtha resulted.

The Tifo catalysts require no supporting material but can becornposited; if desired, with porous or non-porous supports such askiesclguhr, alumina, titania, zirconia, chromia, charcoal, silica gel,silica beads, glass beads, or the like, andi'may be employed withconventional pelleting aids for the purpose of producing catalystpellets in conventional machinery. The Tifo catalystsmay contain variouspromoting metal oxides in proportions between about 0.5 and about 20percent, based on thetotal weight of catalyst, for example oxides ofmetals selected from subgroups 5 and 6 of the periodic table, viz.oxides of V, Nb, Ta, Cr, Mo, W; group 2 metal oxides such asZuO or MgO;group 8 metal oxides such as the oxides of iron, cobalt, jiiclrel orplatinum. r

Although certain specific uses of Tifocatalysts have been describedabove, it should be noted that they are active catalyst for variousconversions, particularly of hydrocarbons, which have heretofore beencatalyzed by acidic catalysts (proton or Lewis acids) such as sulfuricacid, hydrofluoric acid, liquid or dry phosphoric acids, AlCl-g, acidicsilica-alumina catalysts, active clays, and the like. Thus they may beemployed for the cracking of heavy naphthas or gas oils at hightemperatures, decolorization of petroleum fractions, removal ofdiolefinic components from cracked gasolines, polymerization ofnormallygaseous olefins, alkylation of aromatic hydrocarbons orheterocyclic compounds such'as thiophene, illran and the. like,isomerization of .methylparafiins such as Z-methylpentane, isomerizationof xylenes and dehydrogenation reactions; for example dehydrogenation ofcumene to producealpha-methylstyrene.

The catalysts produced by the present invention may also beemployedforthe interaction of olefins with hydrogensulfide Ito produce mercaptans;the isomerization 'of olefins, e. g, of l-butene to 2-butene; theinteraction of 'olefins, carbon monoxide. andsteam to produce carboxylicacids the polymerization of olefin oxides; the

interaction of alcohols or mercaptans with olefin oxides to produce.polyalkoxy derivatives thereof; the dehydrationof alcohols to produceolefinsand ethers; the dehydration '0f 1,3-butylene. glycol. to producebutadieuc; the reactions ofolefins with carboxylic acids to form esters,etc.

When. it becomes necessary to regenerate the Tifo catalyst by reason ofthe accumulation thereon of hydrogen-deficient carbonaceousmaterials orother catalysisinhibiting materials, this may be accomplished bycontacting the catalyst with oxygen-containing gases such as air or fluegases containing 1 to 10 volume percent oxygen at temperatures betweenabout 400 C. and about 500 C. and'atrnospheric pressure for about /2 toabout 0mm. Alternatively, partially spent catalyst may h aeaao'retreated with hydrogen at temperatures between about 350 C. and about 500C. under a hydrogen pressure of at least about 500 p. s. i., for example500 to 2000 p. s. i., for about /2 to 24 hours. If desired, theoxidation and reduction treatments may be performed in succession. Also,as a preliminary to the above-mentioned regeneration treatments, it maybe desirable to extract the catalyst with a hydrocarbon solvent such asbenzene, pentane, hexane, or the like, at temperatures between about 50and about 200 C. under pressure sufiicient to maintain the extractant inthe liquid phase, in order to remove extractable hydrocarbon residuesfrom the Tifo catalyst.

Having thus described our invention, what we claim 1. A process for thepreparation of a self-supporting solid material which is a catalyst forthe polymerization of propylene, which process comprises heatingreagents consisting essentially of titanium dioxide and triphosphoricacid in a weight ratio between about 0.1 and about 2 at a temperaturebetween about 240 C. and about 600 C. in order to effect an exothermic,water-producing reaction.

2. The process of claim 1 which comprises initiating reaction at atemperature between about 240 C. and about 350 C. and thereafter heatingthe reaction mix- 6 ture to a temperature of at least about 380 C., butnot in excess of about 600 C., thereby producing a hard, solid catalyticmaterial.

3. The process of claim 1 wherein the weight ratio of titanium dioxideto triphosphoric acid is between about 0.25 and about 1.3 and thereaction temperature is between about 240 C. and about 350 C.

4. The process of claim 1 wherein the weight ratio of titanium dioxideto triphosphoric acid is between about 0.25 and about 1.3.

5. The process of claim 1 wherein the triphosphoric acid is employed asa mixture with other phosphoric acids.

6. The process of claim 4 wherein said mixture contains about 50 weightpercent of triphosphoric acid.

References Cited in the file of this patent UNITED STATES PATENTS MavityAug. 25, 1953 Bielawski et al. Oct. 20, 1953 25 try, vol. 8, 1928, page945.

1. A PROCESS FOR THE PREPARATION OF A SELF-SUPPORTING SOLID MATERIALWHICH IS A CATALYST FOR THE POLYMERIZATION OF PROPYLENE, WHICH PROCESSCOMPRISES HEATING REAGENTS CONSISTING ESSENTIALLY OF TITANIUM DIOXIDEAND TRIPHOSPHORIC ACID IN A WEIGHT RATIO BETWEEN ABOUT 0.1 AND ABOUT 2AT A TEMPERATURE BETWEEN ABOUT 240*C. AND ABOUT 600*C. IN ORDER TOEFFECT AN EXOTHERMIC, WATER-PRODUCING REACTION.